Thank you for the excellent review and critique. Excellent points all.
Re: Skill checks. It was definitely *not* written under 3.5, though I can see how some of the skill checks might point that direction. In general, it is a failing of mine to err on the side of DCs being too high. My cohorts at GG do a good job in dialing back most my skill check calls, but a few still slip though.
However, a few points in my defense. Feel free to take or leave them:
I wouldn't argue that the skill DCs are fair. In fact, mine are often deliberately unfair. If a non-thief PC reaches the point where he has to make a skill check, he's likely already down the wrong road, having missed the chance to solve the challenge via roleplaying.
So whither the skill check requiring either skilled climber or a nat 20 + 18 Dex? I wrote it with visions of a sheer pit, slick with muck. Literally impossible for all but an insanely talented (or skilled) climber to free climb without tools. (And in Colorado, I know some of those folks. And our climbing skills radically differ.)
Fair? No. Just as not every fight is winnable, not every skill check is make-able. PC / player discretion is key. Fortunately there is the other way out of the passage. Or, hopefully, someone brought rope.
Anyhow, that was the rationale / logic behind it.
You'll see a similar climb check Sailors. I remember Joseph coming to me, saying, "Harley, the climb check is too high! It's almost impossible!" To which my response was, "It's an overhung, crumbling tower. They are untrained, without gear, climbing in sandals or bare feet. Yes, it is nearly impossible."
If memory serves, we dialed it back a little, but it is still a really difficult check.
The lesson? My boss agrees with you. And I still went with the high check.